package com.hit.basmath.interview.top_interview_questions.hard_collection.dynamic_programming;

/**
 * 312. Burst Balloons
 * <p>
 * Given n balloons, indexed from 0 to n-1. Each balloon is painted with a number on it represented by array nums. You are asked to burst all the balloons. If the you burst balloon i you will get nums[left] * nums[i] * nums[right] coins. Here left and right are adjacent indices of i. After the burst, the left and right then becomes adjacent.
 * <p>
 * Find the maximum coins you can collect by bursting the balloons wisely.
 * <p>
 * Note:
 * <p>
 * You may imagine nums[-1] = nums[n] = 1. They are not real therefore you can not burst them.
 * 0 ≤ n ≤ 500, 0 ≤ nums[i] ≤ 100
 * <p>
 * Example:
 * <p>
 * Input: [3,1,5,8]
 * Output: 167
 * <p>
 * Explanation: nums = [3,1,5,8] --> [3,5,8] -->   [3,8]   -->  [8]  --> []
 * coins =  3*1*5      +  3*5*8    +  1*3*8      + 1*8*1   = 167
 */
public class _312 {
    public int maxCoins(int[] iNums) {
        int[] nums = new int[iNums.length + 2];
        int n = 1;
        for (int x : iNums) if (x > 0) nums[n++] = x;
        nums[0] = nums[n++] = 1;

        int[][] dp = new int[n][n];
        for (int k = 2; k < n; ++k) {
            for (int left = 0; left < n - k; ++left) {
                int right = left + k;
                for (int i = left + 1; i < right; ++i)
                    dp[left][right] = Math.max(dp[left][right],
                            nums[left] * nums[i] * nums[right] + dp[left][i] + dp[i][right]);
            }
        }

        return dp[0][n - 1];
    }
}
